Mirrors have been in existence for years and have been used in interior building applications such as, for example, in bathrooms, as decorations, etc.; for exterior applications such as, for example, in concentrating solar power (CSP) and concentrating photovoltaic (CPV) applications, as well as in secondary reflector panels (SRPs); as well as handheld vanity and a host of other products. Mirrors generally are either (a) first surface minors, where the mirror coating is provided between the viewer and the supporting glass substrate, or (b) second surface mirrors, where the supporting glass substrate is interposed between the viewer and the mirror coating. See, for example, U.S. Pat. Nos. 7,276,289 and 7,678,459; U.S. Publication Nos. 2006/0077580; 2007/0178316; 2008/0073203; 2008/0164173; 2010/0229853; 2011/0176212; and 2011/0176236; as well as U.S. application Ser. No. 12/923,836, filed on Oct. 8, 2010. The entire contents of each of these patent documents are hereby incorporated herein by reference.
Many second surface mirrors include silver-based reflecting layers. Silver is highly reflective in the visible and infrared ranges, therefore making it a good choice from a total reflectance perspective. And because silver is a noble metal, it tends to react with other elements a relatively low amount. Because of these properties, and as one common example, second surface silver mirrors have widely been used as home mirrors since 1835, when the silvering process was discovered. Although the chemistry of the wet silvering process has significantly changed since then, the concept remains the same: The rear side (second surface) of the glass substrate is wet-coated with a shiny film of reflective silver, which is then covered with a protective layer of paint to prevent tarnishing and corrosion.
Unfortunately, however, silver is quite expensive. It also is not particularly durable and, for example, is subject to corrosion when exposed to even building interior environments. Durability problems can be overcome with silver-inclusive minors, however, by applying one or more layers of protective paint. Yet these paints are sometimes expensive and, at a minimum, inject time delays in the process because they need to be coated and dried and sometimes re-coated and re-dried. Wet coating techniques also are “messy” and potentially hazardous to humans. Even silver production itself is known to be an environmentally unfriendly process, as it is known that (for instance) about two-thirds of the global silver production is accompanied by a substantial release of mercury.
Thus, it will be appreciated that there is a need in the art for improved minors and/or methods of making the same.
Relatively recently, physical vapor deposition (PVD) techniques such as, for example, sputtering, have been used to efficiently deposit aluminum (Al) minors. It is for example known to replace the silver in a minor with the aluminum. Reflectance in at least the visible range remains high, notwithstanding this substitution.
Despite the fact that the Al is highly reactive, it possesses a natural defense mechanism against corrosion and tarnishing, e.g., by means of a very thin, very stable, and highly transparent oxide layer that forms at its surface. The presence of this oxide layer helps to prevent the rest of the Al from further oxidation. The sputtering process is also much more environmentally friendly compared to silvering. And because aluminum is the third most abundant element in nature and the most abundant metal in the Earth's crust, it tends to be much less expensive than silver. Indeed, a 1:600 cost ratio is common.
Certain example embodiments relate to a second-surface sputtered thin-film mirror deposited on glass and protected with an adhesive tape. The tape replaces the paint backing that conventionally is used in the minor industry to help protect the reflecting member of the mirror from the ingress of moisture. The final layer of the thin film layer stack is selected so as to help make its interface with the tape less sensitive to moisture. Because the safety tape can remain adhered to the layer stack even in high humidity environments, such mirrors may be used in a potentially broader array of applications and/or environments such as, for example, bathrooms, interior and/or exterior applications in areas where there are humid climates, etc. In one of the example embodiments, the tape is a safety tape. Methods of making the same also are provided.
In certain example embodiments of this invention, a mirror is provided. The minor includes a glass substrate. A multilayer thin film coating is supported by the substrate. The multilayer thin film coating comprises, in order moving away from the substrate: a first dielectric layer, a metallic or substantially metallic layer comprising aluminum, and a second dielectric layer, with the second dielectric layer being the outermost layer of the thin film coating and having a contact angle of at least 40 degrees. An adhesive material is disposed directly over and contacting the outermost layer of the multilayer thin film coating.
In certain example embodiments of this invention, a mirror is provided. The minor includes a glass substrate. A multilayer thin film coating is supported by the substrate. The multilayer thin film coating comprises a metallic or substantially metallic layer comprising aluminum sandwiched between inner and outer dielectric layers, with the inner dielectric layer being located between at least the substrate and the metallic or substantially metallic layer comprising aluminum. An adhesive tape is directly over and contacting an outermost layer of the multilayer thin film coating. The adhesive tape is adapted to survive seven day exposure to an 85 degree C. temperature at 85% relative humidity, as well as seven day exposure to a 49 degree C. temperature at 100% relative humidity, without peeling away from the outermost layer of the thin film coating.
In certain example embodiments of this invention, a method of making a mirror is provided. At least the following layers in the following order are sputter-deposited on a glass substrate to form a coating: a first dielectric layer, a metallic or substantially metallic layer comprising aluminum, and a second dielectric layer. The second dielectric layer is the outermost layer of the thin film coating and has a contact angle of at least 40 degrees. An adhesive material is applied over and contacting the outermost layer of the multilayer thin film coating.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.